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1. Field of the Invention
The present invention relates generally to exhaust mufflers for internal combustion engines, and more particularly, to an in-line marine exhaust muffler having an improved conical silencing element for inserted installation into the exhaust pipe connected to an internal combustion engine on a marine vessel.
2. Description of Related Art
Marine vessels are typically configured with a propulsion system having an internal combustion engine mounted internally within the vessel hull. Exhaust generated by the engine is commonly routed through exhaust conduit to the stern or rear of the vessel via one or more exhaust ducts and is discharged through one or more exhaust ports formed in the transom. One or more silencers may be installed within the exhaust duct(s) to silence noise associated with the engine and exhaust gases.
A variety of structures are known in the background art for use in silencing marine exhaust noise. The present inventor has invented a number of novel marine exhaust components that have greatly improved the silencing and efficiency of marine exhaust systems. Among those inventions developed by the present inventor are: U.S. Pat. No. 4,918,917 for a Liquid Cooled Exhaust Flange; U.S. Pat. No. 5,196,655, for a Muffler for Marine Engines; U.S. Pat. No. 5,228,876, for a Marine Exhaust System Component comprising a heat resistant conduit; U.S. Pat. No. 5,262,600 for an In-line Insertion Muffler for Marine Engines; U.S. Pat. No. 5,444,196 for an improved In-line Insertion Muffler for Marine Engines; U.S. Pat. No. 5,504,280, for a Muffler for Marine Engines; U.S. Pat. No. 5,616,893, for a Reverse Entry Muffler With Surge Suppression Feature; U.S. Pat. No. 5,625,173, for a Single Baffle Linear Muffler for Marine Engines; U.S. Pat. No. 5,718,462 for Muffler Tube Coupling With Reinforcing Inserts; and U.S. Pat. No. 5,740,670, for a Water Jacketed Exhaust Pipe for Marine Exhaust Systems.
The background art further includes U.S. Pat. No. 5,824,970, issued to Garcia, for a conical marine engine silencer having an apertured baffle and weir plate. The Garcia device is generally depicted in FIG. 1 herein. The device includes a conical silencer element located within an exhaust duct, and a weir plate. The silencer element has apertured surfaces that are inclined to the flow of the exhaust gases in the duct. The apertured surfaces define an internal cone angle between 15xc2x0 and 30xc2x0, and the apertured surfaces of the silencer element preferably form an angle with the walls of the exhaust duct of between 5xc2x0 and 20xc2x0. The weir plate comprises a continuous, non-perforated plate extending generally axially to the conical silencer element body. The marine engine silencer disclosed by Garcia fails to disclose a conical silencer element that optimizes noise reduction and exhaust gas cooling. The Garcia device also fails to disclose means for optimizing noise reduction and exhaust gas cooling through use of a silencer structure configured to cause exhaust gas to experience reverse gas flow (e.g. in a partially upstream direction). Garcia also fails to disclose a silencing element having an aperture configuration optimized for silencing. Finally, Garcia fails to disclose dimensional parameters for the silencing element that are optimized relative to engine displacement to avoid resonant vibration.
Accordingly, there exists a need for an improved marine engine muffler that optimizes noise reduction by incorporating a structure that forces exhaust gas to follow a reverse flow path. In addition, there remains a need for an improved marine engine muffler having a silencing element with inclined surfaces and an aperture configuration for maximizing exhaust gas silencing. There further exists a need for an improved marine engine muffler having a conical silencer element with dimensional characteristics specifically selected to eliminate excessive vibrational responses associated with fluctuations in exhaust gas flow and resonant frequency dynamics.
The marine engine muffler of the present invention overcomes the disadvantages of the exhaust silencing devices of the background art by providing a marine engine muffler that includes at least one silencing element having at least one surface inclined to the general direction of exhaust gas flow and having a series of elongate slotted apertures disposed circumferentially lengthwise. It has been found that the alignment of elongate slotted apertures in a direction that is perpendicular to exhaust flow (e.g. flow path shown by arrow) provides improved silencing of exhaust gas compared to the prior art muffler shown in FIG. 1 (e.g. slotted apertures disposed in an axial configuration). The conical silencing element is specifically sized and/or tuned to avoid resonant vibration within the operational RPM range of the engine. The conical silencing element is further sized relative to the combined displacement of the engine and/or cylinder bank to avoid problems associated with reflected pressure waves inherent in upstream exhaust system components. The slotted apertures are preferably bounded and defined by angled sidewalls such that exhaust gas flowing through said apertures is forced to travel in a path that is angled in a reverse direction relative to the overall exhaust flow path.
Accordingly, it is an object of the present invention to provide an improved muffler for internal combustion engines.
Another object of the present invention is to provide an improved conical silencing element for engine mufflers.
Still another object of the present invention is to provide an improved conical silencing element having slotted apertures configured so as to require exhaust gas flowing therethrough to follow in a reverse or serpentine flow path.
Yet another object of the present invention is to provide a conical silencing element for marine a muffler that is tuned to avoid resonant vibration throughout the entire RPM range of the associated marine engine.
In accordance with these and other objects that will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.